1. Field of the Invention
This invention relates to polyamides prepared by reacting a monomer selected from unsaturated carboxylic acids and esters and anhydrides of unsaturated carboxylic acids, and at least one amine.
2. Description of the Related Art
It is well known that the physical properties of an organic polymeric material can be altered by introducing specific functional groups into the polymer backbone. For instance, polymeric materials that can conduct electricity, that are magnetic, or that change some property such as color or refractive index under the influence of various external factors such as light, pressure, electric fields, magnetic field, pH changes, or temperature alterations have been prepared by adding functional groups to the polymer backbone. In all of these applications, one critical requirement is that some of the functional groups along the polymer backbone be aligned in a regular repeating fashion with very high density. Polymeric materials with very different properties can be made depending on the choice of the functional groups. Electron donor-acceptor pairs can be conductive or have optical properties that are influenced by electric or magnetic fields. An array of negatively charged groups is a typical arrangement sought for conducting organic polymers where the charge carriers are metal ions and protons. Hydrogels can be formed if charges are present on the side chains. Materials with special conductive, magnetic or electro-optical properties can be fabricated from polymers having specialized aromatic side chains.
In the background section of PCT International Publication Number WO 00/17254, several methods for introducing side chains to a main chain of a polymer are discussed and critiqued. For instance, it is reported in this document that one strategy for introducing side chains to a main chain of a polymer is to add the side chains to the preformed main chain. It is noted however, that this is generally not satisfactory because of the lack of predictability and reproducibility of stoichiometry, under-derivitization for stearic reasons, difficulty in accessing the interior of the polymer, poor solubility of the polymer, and inefficient coupling reactions. It further reported in WO 00/17254 that an alternative method for introducing side chains to a main chain of a polymer is to attach the desired side chain to each monomer prior to chain formation. It is stated that this method is generally more efficient but the subsequent coupling of the monomers often requires activating groups to be attached to one or both coupling sites.
WO 00/17254 provides one solution to the aforementioned problems associated with introducing side chains to a main chain of a polymer. In WO 00/17254, there is disclosed a process for synthesizing a novel polyamide from unsaturated lactones and amines. In the polymerization reaction, the condensation of a lactone with a variety of monofunctional or bifunctional amines is followed by ring opening of the resulting lactone to give a polyamide. The resulting polyamide has a regular, sequential alignment of side chains along the polyamide backbone. The polymerization process can produce cationic, anionic or neutral polymers depending on the nature of the side chain attached to the main chain of the polymer. It is reported that the side chains can be among other things: a very long alkyl chain which generates a bipolar structure; a molecular system with special electrical properties; a polyamine with metal complexation properties; or a carboxylate with cation exchange or capture properties. The disclosed process provides a good general method for the assembly of a continuous array of side chains along a polymer backbone in a quick and efficient manner, does not require activation of groups of the monomer, does not produce any by-products that have to be eliminated, proceeds under mild conditions, is compatible with a large spectrum of functional groups including alcohols, acids, phosphate groups, sulfonates, nitrites, amides and amines, can be carried out in a wide variety of solvents from aprotic solvents to water, and uses renewable resources instead of materials derived from fossil fuels.
While the polymerization process described in WO 00/17254 provides one solution to the aforementioned problems associated with known methods for introducing side chains to a main chain of a polymer, there is one disadvantage with the polyamide polymerization process of WO 00/17254. Specifically, the starting monomers for the polymerization process can be more expensive than other commercially available monomers. Therefore, there is a need for a less costly alternative monomer that produces a polyamide having a regular, sequential alignment of side chains along the polyamide backbone. Also, there is a need for a less costly polyamide material compared to the class of polyamides disclosed in WO 00/17254.
The foregoing needs in the art are met by a polyamide prepared by reacting a monomer selected from unsaturated carboxylic acids, esters of unsaturated carboxylic acids, anhydrides of unsaturated carboxylic acids, and mixtures thereof, and a first amine to form an intermediate reaction product in the reaction mixture, wherein the first amine is selected from RR1NH, RNH2, RR1NH2+, RNH3+ and mixtures thereof, wherein R and R1 can be the same or different and each contain between about 1 and 50 carbon atoms and are optionally substituted with heteroatoms oxygen, nitrogen, sulfur, and phosphorus and combinations thereof, and then reacting the intermediate reaction product and a second amine to form a polyamide, wherein the second amine is selected from R2R3NH, R2NH2, R2R3NH2+, R2NH3+ and mixtures thereof, wherein R2 and R3 can be the same or different and each contain between about 1 and 50 carbon atoms and are optionally substituted with heteroatoms oxygen, nitrogen, sulfur, and phosphorus and combinations thereof, wherein multiple of the R, R1, R2, and R3 are in vertically aligned spaced relationship along a backbone formed by the polyamide.
In one version of the invention, the monomer is selected from maleic anhydride, maleic acid esters, and mixtures thereof. In another version of the invention, the first amine is an alkylamine, such as tetradecylamine, and the second amine is a polyalkylene polyamine, such as pentaethylenehexamine. In yet another version of the invention, the first amine and the second amine are olefinic or acetylenic amines, such as the reaction products of an alkyldiamine and an acetylenic carboxylic acid. In an example embodiment of the invention, the polyamide is prepared by reacting the monomer and the first amine in a molar ratio of from 1:0.05 to 1:1 and adding the second amine in a molar ratio of monomer to second amine of from 1:0.05 to 1:1. The first amine and the second amine may be the same or different depending on the desired polyamide structure.
In one example embodiment of the invention, the polymerization process produces a polyamide of the formula: 
wherein n is between about 50 and 10,000, wherein x is an integer in the range of 0 to 20, wherein y is an integer in the range of 0 to 20, wherein R contains between about 1 and 50 carbon atoms and is optionally substituted with heteroatoms oxygen, nitrogen, sulfur, and phosphorus and combinations thereof, wherein R1 contains between about 1 and 50 carbon atoms and is optionally substituted with heteroatoms oxygen, nitrogen, sulfur, and phosphorus and combinations thereof, wherein multiple of the R and R1 are in vertically aligned spaced relationship along a backbone formed by the polyamide, and wherein R and R1 are neutral, positively charged or negatively charged. In one version of the polyamide of the invention, R is alkyl. In another version of the polyamide of the invention, R1 is polyalkylenyl polyamine. In yet another version of the polyamide of the invention, R1 is an olefinic or acetylenic amino group.
The polyamide of the invention may be crosslinked with a crosslinking agent containing at least two functional groups capable of reacting with amino groups, such as isocyanate compounds having 2 or more xe2x80x94Nxe2x95x90Cxe2x95x90O groups, aldehyde compounds having 2 or more xe2x80x94CHO groups, phosphines having the general formula (A)2P(B) and mixtures thereof, wherein A is hydroxyalkyl, and B is hydroxyalkyl, alkyl, or aryl, and epoxy resins having epoxide end groups.
A polyamide in accordance with the present invention can be tailored for use in many different practical applications. For example, proper selection of two different amines for inclusion in the polymer will create a two-dimensional structure such that one side of the polyamide is non-polar or lipophilic and the other side of the polymer is polar or hydrophilic. Proper selection of the amines can also cause the polyamide to: (1) act as a hydrogel, (2) act as a flocculent, (3) provide surfaces that do not scale, (4) provide surfaces that are more bio-compatible, (5) provide surfaces that bind metals, (6) provide a reducing environment for reducing metal ions to a base metal, and (7) provide a material for use in micropatterning for electronic device manufacturing.
The polyamide, whether crosslinked or not crosslinked, is particularly useful as a coating for a substrate. In one coating application, the polyamide is used to coat a polymeric substrate which may comprise a natural polymer such as cellulose, or a synthetic polymer such as polyethylene, polypropylene, polyvinyl chloride, polyurethane, silicone rubber, polytetrafluoroethylene, or any derivative of these polymers. In another coating application, an antithrombotic agent (i.e., a material that inhibits thrombus formation), such as heparin, is bonded to the polyamide coating to produce an article suitable for medical applications in which the article contacts blood. (As used herein, xe2x80x9cantithromboticxe2x80x9d and xe2x80x9cnon-thrombogenicxe2x80x9d refer to any material which inhibits thrombus formation on a surface.) In yet another coating application, the polyamide is used to coat surfaces in order to suppress biofilm formation. In still another coating application, the polyamide is used as an thin conductive film for electronic devices. Additionally, the polyamide may be used to coat oil and gas lines.
These and other features, aspects, and advantages of the present invention will become better understood upon consideration of the following detailed description, drawings, and appended claims.